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Electric antennas are still large structures (approximately 1m for 300 MHz operation), and have so far eluded the miniaturization trend common in the electronics industry. This is due in large part to an impedance mismatch with free space, and an increase in system losses from ohmic heating as antenna dimensions shrink. Recent work has proposed using multiferroic heterostructures to create small energy efficient antennas. This idea was first explored by Rowen’s 1961 paper on electromagnetic (EM) radiation from YIG, and Mindlin’s 1973 paper on radiation from quartz. Since then limited work has looked at EM radiation from adaptive materials, and there are currently no analytical models describing such a device. This presentation provides an analytical model to examine small mechanically powered energy efficient antennas.
An analytical framework is provided that couples elastodynamics and electrodynamics using piezoelectric and piezomagnetic constitutive behavior. This approach uses an eigenmode expansion of the undamped longitudinal vibrations in a prismatic rod to describe EM radiation from each harmonic mode. The problem is reduced to examination of damped harmonic oscillators, and EM radiation is shown equivalent to an effective volumetric strain-rate dependent damping. This approach provides the frequency response of a mechanical antenna, and demonstrates important scaling behavior relative to conventional antennas. Resonant analysis leads to simple closed form expressions for antenna efficiency, and leads to a metric directly comparing mechanical and conventional antennas, facilitating both material selection and device design. To summarize, this presentation provides a first look at the strain-mediated control of wireless communications.
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